1. Field of the Invention
The present invention relates generally to an impulse radio-based ultra wideband (IR-UWB) wireless communication system, and more particularly, to an IR-UWB communication system capable of performing communication at a rate of up to several Mbps in a local area of several tens of meter while consuming low power and supporting low complexity by way of a receiver based on energy detection scheme, a transmitter including an integrated impulse generator, and synchronization acquisition and tracking schemes using a 1-bit digital sampler and a bit decision window.
2. Description of the Related Art
Unlike a wireless communication system using a continuous sinusoidal wave, an impulse radio-based ultra wideband (IR-UWB) communication uses an impulse-like signal that has less than several nanosecond (10−9 second) pulse width in time domain and an ultra wideband frequency spectrum in frequency domain. Since an IR-UWB system makes use of an extreme short pulse in time domain and does not require some RF components such as mixer, it has low complexity and its power consumption can be dramatically reduced. Thus, data communication of low power consumption up to several tens of Mbps is theoretically possible. Since an impulse is used, the IR-UWB communication can also be used in implementing a system having an exact time precision characteristic, and thus can be used in implementing a low power consumption/low data rate/high accurate ranging and precision positioning and tracking system.
As a first example of the prior art, the Korean Electrotechnology Research Institute disclosed a wireless communication transmitter using a method of generating Gaussian pulses and ON-OFF Keying (OOK) modulation (Korean Patent Number 1004700290000). The object of the invention is to simplify a device and reduce power consumption for transmission. The wireless communication transmitter includes a Gaussian mono cycle generator, a binary random data generator, a switching means, a filtering means, an amplification means, and an antenna. The Gaussian mono cycle generator generates ultra wideband pulses having a predetermined interval using the ultra wideband characteristics of a Gaussian mono cycle pulse in place of a continuous wave such as a sine wave, used as a carrier in a prior art wireless communication transmitter. The impulse is generated by a microprocessor or a rectangular wave generator at the rising edge of an input rectangular wave.
An ultra wideband pulse string generator (Korean Patent Number 1005201500000), disclosed by Samsung Electronics Co., Ltd., is a more simplified wireless communication system including a chip type impulse generator as a second example of the prior art. The second example of the prior art proposes a method of designing the chip type impulse generator, and includes using a latch to coerce an impulse generator to have a time interval in response to an input signal. The method relates to a signal generation method pertaining to a method of BPSK modulation, in which a signal is inverted each time a data value changes.
According to the prior art wireless communication systems, various impulse communication methods are essential in order to activate the UWB technique, but they have a problem that the construction of low complexity and low power consumption communication system is not simple because the first example is to use a module-based impulse generator and the second one is to need a complex IR-UWB receiver.
The other examples of the prior art are as follows: U.S. Pat. No. 6,925,109, issued by Aug. 2, 2005, U.S. Pat. No. 4,743,906, issued by May 10, 1988, and U.S. Pat. No. 4,641,317, issued by Feb. 3, 1987.
For IR-UWB system of low power consumption and low complexity from the viewpoint of implementation, chip-based impulse generation technology consuming low power and supporting low complexity is required. Also, in an ultra wideband impulse receiver, a digital signal recovery unit is the most important element in a fundamental arrangement. An ultra wideband signal in a time domain has a duration less than several nanoseconds (10−9 second). Accordingly, the ultra wideband impulse may be converted into a digital signal through various methods. However, it is difficult to implement the conversion in practice due to the high complexity, cost, and power consumption of the system. Consequently, the prior art impulse communication systems do not provide a new method for restoring an ultra wideband impulse signal to a digital signal, and instead use a general ultra wideband high-speed analog-to-digital converter (ADC). In most cases, the bandwidth of an impulse is equal to or greater than 500 MHz, and thus the ADC should have a bandwidth greater than 1 GHz. Since the prior art impulse communication systems use a high-speed ADC having a bandwidth greater than 1 GHz and a sample rate of several Gsps (samples per second) and a precise phased lock loop (PLL), they require an expensive device and use a lot of power to manage the expensive device.
Furthermore, since exact time synchronization with respect to impulse signals requires a complicated synchronizing circuit, and reduces the advantages of the ultra wideband impulse system having low cost and low power consumption characteristics, in signal processing, simple detection and tracking technology of recovered symbol is very important.